"I've seen so many, not just kids, but families singing along to every word of every song. And people accepting me in such a short amount of time.

"You know I knew that Rihanna headlined yesterday and she's been someone that's built a career over many albums and many years and to be in a position where I'm headlining the next day after her has been insane and a moment I won't forget."

The singer's headline set also featured several surprises for the sold-out O2 audience as singer-songwriter James Morrison and rapper Wretch 32 each joined Jessie J on stage for performances of 'Up' and 'Price Tag', respectively.